[Evaluation of the tissue diffusion capacity of antibiotics in lower limb ischaemia]

Abstract

Introduction: The aim of the study was to assess whether the penetration of antibiotics is affected by decreased tissue perfusion in patients with limb ischaemia, thus reducing its concentration in tissues below the minimum inhibitory concentration (MIC) breakpoints of antibiotics for different microorganisms.

Methods: Prospective study. Candidates for major amputation with critical lower limb ischaemia and an infection on antibiotic treatment, were included. Three levels of perfusion in the lower limb were determined by measuring the transcutaneous oxygen pressure (TcPO2). A central line blood specimen, as well as biopsies of the skin, muscle, and bone, were taken at each perfusion level. The antibiotic concentration was determined using HPLC.

Results: The total number of cases was 61 (46 patients): 6 clindamycin, 9 vancomycin, 8 linezolid, 18 levofloxacin, 9 ceftazidime, and 11 meropenem. Statistically significant differences were found in TcPO2 at all levels (ANOVA, P=.000). The vancomycin, levofloxacin and ceftazidime skin concentration depends on perfusion. Vancomycin and levofloxacin diffusion in bone is worse than in other tissues. Ceftazidime concentration does not exceed the MIC breakpoint of Pseudomonas aeruginosa in ischaemic tissues.

Conclusions: Meropenem and linezolid diffuse in all tissues, regardless of perfusion, reaching concentrations above the MIC of the target microorganisms, ensuring its effectiveness in ischaemic tissues.

Keywords: Amputación; Amputation; Antibiotics; Antibióticos; Diffusion; Difusión; Ischaemia; Isquemia.